4
Optimizing the Design of Combat Rations
Irwin A.Taub1
INTRODUCTION
As Operation Desert Storm demonstrated, success on the battlefield depends on superior tactics, high-tech advanced equipment, and high-performing troops who can, under very stressful conditions, properly use the equipment to achieve the tactical objectives set for them. High performance, in turn, depends on the soldiers having—besides good training and suitable protective clothing—nutritionally optimized combat rations.
Accordingly, it is the responsibility of the food and behavioral scientists at the U.S. Army Natick Research, Development and Engineering Center (referred to as Natick), working closely with the nutritionists and physiologists at the U.S. Army Research Institute of Environmental Medicine, to optimize the design, processing, and storage of combat rations. If this responsibility is discharged properly, soldiers will consume these rations more completely, they will enjoy them more, their morale will be boosted, and they will ingest special constituents that will help them to perform well even under unusual circumstances and in many different battlefield situations.
This chapter highlights the factors crucial to designing combat rations and puts into perspective the related research in food science and technology that underlies the development of such rations.
OPTIMIZATION CONSIDERATIONS
Six major factors must be taken into consideration in optimizing combat ration design.
Performance enhancement is the key factor and was the focus of the workshop on which this volume is based. Its relevance is self-evident, and more detail on related research is given below.
Caloric densification is extremely important for situations in which a soldier must have highly compact rations that are also easy to handle. These rations have many calories packed into a very small volume. Some of the components have a caloric density of about 7 kcal/mL. The dairy bar is illustrative.
Component preservation is the basis for providing shelf-stable operational rations in the field. The components must be microbiologically stable, which can be achieved either by destroying all the pathogenic and spoilage microorganisms or by inhibiting their growth. Moreover, even after accomplishing that, one must ensure that the food remains biochemically, physically, and chemically stable. It should have the same structure and appearance after 3 years of storage at a nominal temperature of 27°C (80°F) as it had when it was first produced.
Heating and cooling of such rations is an important consideration, because hot food and appropriately cool beverages affect morale and proper food and water intake.
Unless there is consumer acceptance of the food, it will not be consumed and nutrition could be compromised. Meeting all of the nutritional requirements is predicated upon consumption of the entire ration. Satisfaction with the ration contributes as well to the social well-being of the soldier.
Lastly, quality monitoring by using time-temperature integrators is also important. It makes it possible to ensure that, despite high temperature stresses over long storage periods, the food has the intended attributes and nutrients at the time of consumption.
Details on rations and the research relating to the six factors that are crucial to designing combat rations appear elsewhere (Beard, 1991). Only the work done at Natick on component preservation and on the heating of rations that would not generally be familiar is discussed here, primarily by reference to the combat rations currently under development.
SELF-HEATING INDIVIDUAL MEAL MODULE
A conceptually new self-heating ration is called the self-heating individual meal module (SHIMM) (Figure 4–1). In many ways it is similar to the Meal Ready-to-Eat (MRE) and has some of the MRE components, including the pouch bread, which remains stable and does not become stale even after 3 years of storage, and the Desert Chocolate Bar, which will not melt in one’s hands. What clearly distinguishes this ration from the MRE is the placement of the entree item in a polymeric tray that has an integral heater capable of being activated by the pull of a tab. The entire component is actually a two-tray system, with the upper tray containing the separately processed food nested within the lower tray containing the chemical heating system. The high quality and familiar appearance of the components, the convenience of the tray-plate configuration, and the flameless, nonpowered heating contribute to the entree’s and the SHIMM’s appeal.
Component Preservation
With regard to preserving the components so that this combat ration is shelf-stable, all contaminating microorganisms, the pathogenic and spoilage microorganisms, must be destroyed. Two strategies are currently available: irradiation sterilization and thermal sterilization. Irradiation would be particularly suitable for whole-meat food items; thermal processing is used for casseroles, gravy-based items, and vegetables in a brine solution.
In the case of processing by irradiation, the meat is first precooked to a medium rare state to inactivate proteolytic enzymes and to make it ready to eat. It is put into a flexible pouch or a metal container, the air inside the container is evacuated to eliminate the oxygen, and the container is then hermetically sealed. The food components are then frozen and subjected to a high dose of irradiation, equivalent to destroying 12 decades of Clostridium botulinum. (Destruction of a hypothetical population of 1012botulinum spores is the basis for the commercial sterility of irradiation processed and thermally processed packaged foods.)
The irradiated beefsteak shown in Figure 4–2, although used by U.S. astronauts, has not yet been approved for general use in the United States. Over the last 3 years it has been used in South Africa by the South African Army, with very favorable results. Investigators are working toward a generic clearance of this technology by the U.S. Food and Drug Administration so that it can be applied to the production of similar high-quality entree items.
More conventionally, an entree item formulated as a stew or with some gravy to conduct the heat would be subjected to thermal processing. In the case of the Salisbury steak shown in Figure 4–3, the container has a thin cross section, so a whole-meat item could be thermally sterilized without significant overprocessing and without the associated degradation in quality.
Various other thermal sterilization techniques are being explored, including ohmic and microwave heating. With ohmic heating, the passage of an electrical current through the food produces the high temperature needed to destroy the microorganisms; with microwave heating, the microwave energy is absorbed by the water in the food, which increases the water’s temperature, and the heat is transferred from the water to the other constituents. In both cases, the intention is to achieve a high-temperature, short-time exposure, thereby killing the microorganisms but retaining the nutrients and other quality factors of the food.
Self-Heating
With regard to heating the food prior to consumption, the SHIMM utilizes a chemical heating pad—a magnesium-iron material that is embedded in a high-density polyethylene matrix and that is activated by water. The pad is about one-half the length of the lower tray, which also holds a polymeric bag with the activating solution (Figure 4–4). Upon pulling the tab, the soldier rips open the bag, the water comes into contact with the pad, a chemical reaction immediately takes place, and heat is generated. Within 10 min, the soldier has a hot meal.
Consumer Acceptance
With regard to acceptance, it is crucial that the customers (i. e., military personnel) like what they see so they will want to consume the ration. To ensure that favorable reception, the developers of the meals follow a simple principle espoused by behavioral scientists: When receiving the ration, soldiers should perceive a benefit, both nutritionally and gastronomically. Consequently, if there is going to be a positive association with the ration, the visual presentation becomes very important.
Such considerations have been and are being made both in connection with the SHIMM and by further modifying the MRE. One experimental version of a modified MRE is called the FieldBreak (Figure 4–5). Not only is the meal bag colorful and attractive in name and appearance but so are the individually packaged components. It is assumed that the soldier will associate this military food with a well-liked commercial product, which will very likely increase his or her interest in, and consumption of, the ration.
NUTRITIONAL ENGINEERING FOR PERFORMANCE ENHANCEMENT
As indicated initially, the foremost consideration is to nutritionally engineer combat rations to contain performance-enhancing components. Inherent in such efforts is the assumption that there is a fundamental connection between performance and nutrition. Accordingly, a performance-nutrition response surface can be constructed as a guide to ration design.
Basic Performance-Nutrient Concept
To put the basic performance-nutrient concept into perspective, a hypothetical performance-nutrient response surface is shown in Figure 4–6. It plots performance along the z axis, running from 0.5 to 1, where 1 is the “ideal,” however it is defined. Any type of physical or cognitive performance can be normalized in this way and then correlated with particular nutrients. In this case, performance is plotted against the amount of carbohydrates in the ration (along the x axis) as well as against the total number of calories (along the y axis). It is important to note that as one increases the caloric content, the ration package gets heavier; at constant calories, as one increases the carbohydrate content, the package not only gets heavier but it also becomes disproportionately bulkier because of the replacement of the more energy-dense lipids.
These concerns are relevant to optimizing the weight and bulk of rations without compromising performance. Consequently, if an actual surface determined through experimentation looked like the one in Figure 4–6—and some results already obtained (see Chapter 3) imply that it would—then design decisions would be based on the relatively flat portion of the response surface, the flatness indicating approximately comparable performance. A ration with fewer calories and adequate, but not superfluous, carbohydrates would lead to suitable performance while maintaining the weight and bulk of the ration.
Several kinds of nutrients for which there could be a positive link with performance are being considered. They are as follows:
-
Macronutrients
-
Carbohydrates (type and total)
-
Lipids
-
-
Metabolic acids
-
Carnitine
-
Pectin
-
-
Neurotransmitter precursors
-
Tyrosine
-
Phosphatidylcholine
-
The macronutrients, particularly the carbohydrates, are crucial. There is interest in not only total carbohydrates but also in the type of carbohydrates. If the delivery of glucose to the bloodstream could be modulated through a judicious selection of complex carbohydrates, then physical endurance might be extended. The rate and extent of carbohydrate conversion, as reflected perhaps in the glycemic index, will form the basis for future experimentation. Various metabolic acids are important as well, since these may influence carbohydrate and lipid utilization.
Precursors to neurotransmitters, such as tyrosine and phosphatidylcholine, are potential performance-enhancing ingredients. The work of Banderet and Lieberman (1989) has already shown that tyrosine can reduce the severity of the symptoms of high-altitude sickness among susceptible individuals. Zeisel (1990) has suggested that choline is an essential nutrient and has also indicated that muscle function and mental alertness could be improved by increasing the amount of phosphatidylcholine in the diet. The potential importance of choline to performance is evidenced by data from marathon runners (Conlay et al., 1986).
The formulation of rations with optimum levels of such ingredients and without compromising the quality of the food or its acceptance is a fundamental challenge for food technologists.
Goal Programming
The design of diets that can be used experimentally to determine the performance-nutrient link—and, ultimately, to design optimal rations containing the desired nutrients—requires the mathematical approach of goal programming (Hintlian, 1990).
For this purpose investigators use LINDO, which stands for Linear Interactive aNd Discrete Optimization. The illustrative equation in Table 4–1 shows the objective function that must be minimized. LINDO allows one to
impose many kinds of constraints on minimizing this function, so that more than just nutrient composition is taken into account.
Experimental Diets
In using LINDO in connection with the study described by Askew (see Chapter 3) on assessing the influence of total carbohydrates on performance, the level of carbohydrates in each diet had to be fixed, while the levels of protein and fat were allowed to deviate about specified target values. Moreover, the experiment required three isocaloric diets of 3,200 kcal each, with each providing 250, 400, or 550 g of carbohydrates per day. Consequently, for the diet intended to contain 550 g of carbohydrates per day in each of four daily menus, the protein and fat levels were allowed to deviate minimally from target values of 90 g for the former and 116 g for the latter.
Since the acceptance of the diet might be compromised by the presence of too many similar components from among those being used to establish the menus, the following constraints on meal composition were imposed: at least one entree, no more than two fig bars, at least one cereal bar, and no
TABLE 4–1 Illustrative Equation for Minimization of the Objective Function for Obtaining a Diet with Fixed Carbohydrates and Targeted Levels of Fat and Protein within Specified Constraints
more than 250 g of maltodextrin (M 500) from the beverages. These are constraints on the number of units of each component, consistent with the integer solutions computed.
The actual computation involves equations for each nutrient, whether fixed or targeted, taking into account the contributions of individual components to the total, as is illustrated for carbohydrates (Table 4–2). These components with carbohydrates, as illustrated for were configured as food bars, dried items, or baked products. Each has a very specific weight of, for example, 30, 40, or 70 g. Since the solution is constrained to be an integer solution, the program will select none, one, or multiples of each component and will provide a set of optimized solutions, taking the percent carbohydrates into account. These range from 2.1 percent in the beef jerky, to 17.7 percent in the fruit chew, to 50 percent in the cornflake bar, and to 79.7 percent in the strawberry oatmeal bar. The total was to be 400 g in the illustration shown in Table 4–2. A specific constraint was to limit the overall selection to only two flavors of each of the different types of components. Similar computations were made for the diets that contained 250 or 550 g of carbohydrates per day.
For the study described by Askew (see Chapter 3) on assessing the effect of total carbohydrates on performance, the program generated four different daily menus for each of the three carbohydrate levels. A sample menu for Day 1 served to the study group receiving 250 g of carbohydrates is outlined in Table 4–3. Three meals (breakfast, lunch, and dinner) and two snacks (in
TABLE 4–2 Objective Function for Carbohydrates Showing the Contributions to the Total Carbohydrates of Individual Components Whose Weights are Selected in the Optimization Procedure
TABLE 4–3 Sample Menu for the Optimized Experimental Diet Providing 250 g of Carbohydrates on Day 1 of a 4-Day Menu
Meal and Food |
Weight (g) |
|
Breakfast |
||
Life cereal bar |
30 |
|
Nut dairy bar |
40 |
|
Cocoa bar |
30 |
|
Beverage |
13 |
|
Lunch |
||
Creamed chicken chowder bar |
47 |
|
Bacon and cheese shortbread |
25 |
|
Smokecraft Slim Jim |
46 |
|
Almond fig bar |
30 |
|
Beverage |
13 |
|
Dinner |
||
Chicken and rice entree |
70 |
|
Seafood chowder bar |
47 |
|
Fried onion shortbread |
25 |
|
Infused flat bread |
50 |
|
Almond dairy bar |
40 |
|
Beverage |
13 |
|
Snacks |
||
A.M.: |
Cocoa bar |
30 |
Coconut Bear Valley bar |
20 |
|
Beverage |
13 |
|
P.M.: |
Cheese shortbread |
25 |
Vanilla dairy bar |
40 |
the morning and afternoon) were served. The breakfast included a yogurt-based dairy bar, which could be rehydrated to a regular yogurt consistency. The lunch was Spartan compared with that obtained at fast-food outlets, but it included a chicken chowder, a Slim Jim, and a fig bar. More conventionally, the dinner included a very tasty seafood chowder, a well-liked chicken with rice entree, a flat bread (which was infused with lipid to increase calories), and an almond bar for dessert. Although three dairy bars were on the menu, no flavor was duplicated. The adjustable carbohydrates, however, were obtained by using a flavored maltodextrin-based beverage containing 13 g of carbohydrates four times a day. The fixed weight of each component was used, representing one unit of the particular configuration; none was broken into smaller units.
Tailored-Ration System
The goal-programming approach can be applied to designing rations as well. It is particularly suited to the concept of a tailored ration system in which the rations are optimized for various situations that might require different nutrients. The idea is to assemble a situation-specific ration by combining a core module of 1,500 kcal with other supplementary modules. As schematically outlined in Figure 4–7 for four situations, one could add to the core module the following tailored supplements: a hot weather supplement (HWS) for the desert; a cold weather supplement (CWS) for the arctic; a high altitude supplement (HAS) for mountainous terrains; and a snack food supplement (SFS) for general use. The tailored ration shown in Figure 4–7 is for the standard temperate environment.
The modules would be combined to provide the total number of calories and any special nutrients needed for each situation. Two core modules for standard use would provide 3,000 kcal (Figure 4–8). In the case of the arctic situation, the CWS alone would have 3,000 kcal, so the total number of calories associated with one CWS and one core module would be 4,500 kcal. In the case of the high-altitude situation, the HAS could be designed with appropriate calories and with high tyrosine-containing components to meet the needs posed by the low-oxygen and, possibly, low-temperature conditions.
The prototype core module with its components is shown in Figure 4–9. Totaling 1,500 kcal, it could have an entree such as the dehydrated pork and rice, the MRE pouch bread, a meat stick, two compressed cereal bars, two maltodextrin packets (which would be configured as a bar rather than as the powder shown in Figure 4–9), and a dairy bar. Despite having a high caloric density of 6.8 kcal/mL with 56 percent of the calories coming from lipids, the dairy bar is a very popular, highly rated item that can be eaten as is or made into a pudding. It exemplifies components that can be made to meet stringent nutritional needs and still meet stringent consumer expectations.
Depending on what is ultimately learned and confirmed about the link between performance and nutrients, specific ingredients would have to be formulated into suitable components that could be optimally combined into rations appropriate to military situations.
SUMMARY: THE CHALLENGE
As the foregoing indicates, the task for food technologists can be thought of as the performance-nutrient challenge. After the nutritionists and physiologists select the ingredients of greatest potential—those that would have a positive effect on performance—the food technologist would have to ensure that the related ration components are formulated and processed in a compatible and acceptable manner, that these ingredients can tolerate long-term storage, that they can survive digestion and remain physiologically active, and that they can be delivered in a modulated manner to the targeted physiological sites.
If the challenge can be met, then the combat rations will not only contain performance-enhancing nutrients and related constituents, but these nutrients will also be optimally available at the time of consumption and will be fully consumed. The overall goal is to go beyond that challenge so that soldiers who consume such rations will recognize and experience the performance benefits of extended endurance and heightened alertness.
REFERENCES
Banderet, L.E. and H.R.Lieberman 1989 Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Res. Bull. 22:759–762.
Beard, B. 1991 Hot meals in a hot spot: How we feed our troops in Saudi Arabia. Food Technol. 45:52–56.
Conlay, L.A., R.J., Wurtman, K.Blusztajn, I.L.G.Coviella, T.J.Maher, and G.E.Evoniuk 1986 Decreased plasma choline concentrations in marathon runners. N. Engl. J. Med. 315:892.
Hintlian, C.B. 1990 Use of math programming techniques to design experimental diets and military rations. In Abstracts of the IFT (Institute of Food Technologists) Annual Meeting. Chicago: 169.
Srzezinski, A.A., J.J.Wurtman, R.Gleason, T.Nader, and B.Laferrere 1990 D-fenfluramine suppresses the increase calorie and carbohydrate intakes and improves the mood of women with premenstrual syndrome. Obstet. Gynecol. 76:296–301.
Zeisel, S.H. 1990 Choline deficiency. J. Nutr. Biochem. 1:332–349.